Sound amplifier



A. KNUDsEN 1,727,65

Sept.. 19, 1929,

SOUND AMPLIFIER Eiled Oct. 15, 1927 Patented Sept. 10, 1929.

UNITED STATES- PATENT OFFICE.

Lpplloltlol Ilell Uetober 15, 1?, Serial No. 286,471, and. in, Denmark October 16, 1998.

The horns or amplifiers for gramophoues and for radio receiving sets hithertoy used very frequently involve the drawback that the cannot be brought to vibrate with ex- 5 act y the same vibrations as those produced b `the music or speech layed or broadcast. ence, it happens that t e propervibrations .of' the speaking trumpet are heard as .special aliquot. tones whichhave a disturbing and lo sometimes attenuating effect on the tones of the music, so that not all the tones of the piece of music can be heard. The present invention which relates to a horn or loud speaker for gramophones and radio apparatus removes this drawback, so that every tone is 'heard clearly and distinctly without disturbing aliquot tones.

In the accompanying drawing: Fig. 1 is a plan view of a loud speaker according to the invention,

Fi. 2 is a section on the linea-a of Fig.

gig. 3 a section onthe line b-b of Figs. 1 an 2. The vhorn or'speaker in questionis constructedby luing together several pieces of wood in ceci of which is made a hole of a certain form, so that these holes, 'after the joining of the pieces to a speaking trumpet or horn, are in communication with each other and together form in the interior of the speaking trumpet a, cavity suitable for the sound and rather funnelshaped.

1 is the laminated horn or trumpet which at the top has a hole 2 for coaction either with a ton'e arm -for a ramophone or with a telehone receiver or a radio receiving set. rom the hole 2 emerges a nearly funnelsha cavity 3. which irst asses almost horizontally totherside of the orn opposite to the hole'2, where it merges evenly mto a downward sloping cavity 4. This sloping cavity 4 is in communicationwith an opening 5 1 g symmetrically about the vertical center-hilfe ofthe horn. The cavities 3 and 4 and the opening 5 are ofconstantly increasing cross-sectional area from hole 2 onward.

In order to produce a pure tone the cavitiesl 3.

and 4 must have the special form shown. l y .A Yhorn or speaking-trumpet like that de- .side thereof and terminating in a relatively scribed can be placed in the usual vgramophone cabinets. When used for radio receiving apparatus 1t can likewise be built in the said ca inet or in another one s ecially constructed, so Ithat there is room or the radio apparatus in the same cabinet.

I claim as my invention:

An amplifying horn, comprising amultiplicity of veneer laminas glued together to form a single unit, said unit having formed o through its component lamin a sound passage of constantly-increasin circular crosssection throughout, starting om a relatively small hole in the top of the unit toward one large outlet opening which-.extends laterally outward through the front of the unit; the intermediate portion of the passage between said hole and said opening first extendingv horizontally toward t e opposite side of the unit from that in which the holeis located and then sloping downward and merging into said openin I testimony wereof I affix my signature.

ALFRED KNUDSEN. 

